What is the difference between "active" and "passive" immunity in animals?

Active immunity develops from exposure to pathogens, which can occur through natural infection or vaccination. When an animal's immune system encounters a pathogen, it responds by producing specific antibodies and memory cells tailored to that pathogen. This process can take time to build up, but it leads to a long-lasting defense because the immune system retains a memory of the pathogen, allowing for a quicker response during future exposures.

In contrast, passive immunity involves the transfer of antibodies from one animal to another, such as a mother passing antibodies to her offspring through milk or placental transfer. This type of immunity does not create a memory of the pathogen; thus, it is typically short-lived, as the transferred antibodies will eventually break down.

Understanding this distinction is crucial in immunology and veterinary medicine because it informs treatment decisions and vaccination strategies for various animal species.